diff --git a/Lib/fontTools/misc/arrayTools.py b/Lib/fontTools/misc/arrayTools.py
index f2cfac838..ed20230c9 100644
--- a/Lib/fontTools/misc/arrayTools.py
+++ b/Lib/fontTools/misc/arrayTools.py
@@ -6,6 +6,7 @@
 
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
+from fontTools.misc.fixedTools import otRound
 from numbers import Number
 import math
 import operator
@@ -20,10 +21,11 @@ def calcBounds(array):
     ys = [y for x, y in array]
     return min(xs), min(ys), max(xs), max(ys)
 
-def calcIntBounds(array):
+def calcIntBounds(array, round=otRound):
     """Return the integer bounding rectangle of a 2D points array as a
     tuple: (xMin, yMin, xMax, yMax)
-    Values are rounded to closest integer.
+    Values are rounded to closest integer towards +Infinity using otRound
+    function by default, unless an optional 'round' function is passed.
     """
     return tuple(round(v) for v in calcBounds(array))
 
diff --git a/Tests/misc/arrayTools_test.py b/Tests/misc/arrayTools_test.py
index 108b50da2..2610c0fcc 100644
--- a/Tests/misc/arrayTools_test.py
+++ b/Tests/misc/arrayTools_test.py
@@ -1,5 +1,6 @@
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
+from fontTools.misc.py23 import round3
 from fontTools.misc.arrayTools import (
     calcBounds, calcIntBounds, updateBounds, pointInRect, pointsInRect,
     vectorLength, asInt16, normRect, scaleRect, offsetRect, insetRect,
@@ -15,8 +16,13 @@ def test_calcBounds():
 
 def test_calcIntBounds():
     assert calcIntBounds(
-        [(0.1, 40.1), (0.1, 100.1), (49.9, 49.9), (79.5, 9.5)]
-    ) == (0, 10, 80, 100)
+        [(0.1, 40.1), (0.1, 100.1), (49.9, 49.9), (78.5, 9.5)]
+    ) == (0, 10, 79, 100)
+
+    assert calcIntBounds(
+        [(0.1, 40.1), (0.1, 100.1), (49.9, 49.9), (78.5, 9.5)],
+        round=round3
+    ) == (0, 10, 78, 100)
 
 
 def test_updateBounds():